The Chinese president, Hu Jintao, warned that the Communist party was still suffering from corruption and other "growing pains" as the 90-year-old organisation celebrated its anniversary in lavish style at the Great Hall of the People in Beijing.

In a highly choreographed event that was broadcast live across the nation, Hu lauded the achievements of the venerable and vast political party but emphasised the need for greater internal discipline. His message was partly overshadowed by the mysterious absence of his predecessor, Jiang Zemin, from the lineup of senior cadres.

"If corruption does not get solved effectively, the party will lose the people's trust and support. The entire party should stay alert and fully appreciate the long-term complexity and arduousness of the fight against corruption, and make more efforts in fighting corruption and building a clean government," Hu said.

Hu gave little hope, however, to those seeking wider political reform that might curb the power of cadres, some of whom he acknowledged were "incompetent" and "divorced from the people". Instead of radical change, he said, the party needed more internal democracy.

His comments reflect the transformation of the Chinese Communist party, which started in 1921 as a revolutionary organisation with a dozen founders, and is now a technocracy with 80 million members and distinctly aristocratic tendencies. Many senior cadres - large numbers of whom are now the "princeling" sons and daughters of former leaders - use party connections for self-enrichment in an increasingly divided society.

Lacking an electoral mandate, the party has built its legitimacy on managerial competence and national strength, particularly with economic growth and engineering prowess. This week's political celebrations have coincided with the unveiling of three mega-projects: the world's longest sea bridge, which spans the 16 miles (26km) from Qingdao to Huangdao; the world's longest gas pipeline, which stretches 5,400 miles (8,700km) from Xingjiang to Guangzhou; and a new high-speed railway, which cuts the travelling time between Beijing and Shanghai to less than five hours.

In the runup to its own birthday this week, the party has also ramped up the propaganda volume with a series of high-profile events, including a "Red Song" contest in Chongqing that reportedly drew 100,000 people, the premiere of a star-studded historical drama about the founding years, and lavish TV galas. State media have run extensive special issues highlighting the successes of the party in ejecting foreign colonialists, taking power under Mao Zedong in 1959, lifting hundreds of millions out of poverty and maintaining stability.

Little or no mention has been made of the party's failings, including famines that killed tens of millions of people after the Great Leap Forward in the late 1950s, the murderous political chaos of the Cultural Revolution, and the massacre of several hundred protesters after the Tiananmen Square demonstrations of 1989.

Hu only said lessons had been learned. "In some historical periods, we once made mistakes and even suffered severe setbacks, the root cause of which was that our guiding thought then was divorced from China's reality. Our party managed to correct the mistakes by the strength of itself and the people, rose up amid the setbacks and continued to go forward victoriously," he told the thousands of senior cadres gathered inside the Great Hall of the People.

The biggest surprise was the non-appearance of the former president and party leader Jiang Zemin, prompting speculation of illness or a rift within the higher echelons of the party.

The former is more likely, given that Jiang is 84, but he also represents a different strand of opinion about the future direction of the party and the nation. Internal party debates are carried out behind closed doors, but there has long been a divide between those like Jiang on the "right" who favour more deregulation, opening and market reform and those on the "new left" who favour a more interventionist, egalitarian and authoritarian approach. Hu was seen as being closer to the former when he took power in 2002, but he has spent much of his time as state president and party secretary straddling the two camps.